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Ah, yes, read about that in the UH-1H section of the forum.https://forums.eagle.ru/showthread.php?t=201323
I agree with you. I have that campaign already though. But I'm sure it will be fixed soon. In the meantime, I think you can alter the mission in Mission Editor and delete the unit causing the conflict.

Just a small tip.
If you want to play mission 3 then you can edit the mission 3 file.

However, be aware that mission 3 have a bug with the cargo that you need to move, so the suggestion above to skip mission 3 maybe is the best choice..

.. The problem with mission 3 is that the 300kg cargo fly arround like the wind, and even very small swing on the cable will make it fly arround like crazy and even above your rotor... You can start the mission, but you cannot complete/win.

Open up the miz in 7zip or whatever is your favorite zip based program. Extract the "mission" file within. Open that up in notepad++. Remove the line ["F-4E by Belsimtek"] = "F-4E by Belsimtek",Resave the file, make sure not to add any extensions. Paste the file over the old one within the .miz. Close zip program, launch the game, and take a shot of your favorite whiskey for good luck. Otherwise sit and wait for it to get patched because it is already reported.

ED have made every effort to ensure campaigns are reworked if needed for 2.5, our campaign testers have spent a lot of time testing various mission, and as you can imagine it is a huge task.

Any 3rd party campaigns ( ie not made by ED themselves ) will get tweaked also but it requires editing by the 3rd party creator, any issues are being addressed as soon as possible and rolled out in future patches.

Say, I have a 2.5 related campaign question. I bought the Su-27: Ultimate Argument through Steam, back before 2.5 existed, and now it isn't available. I thought it used a Starforce key, how can I get it back? I'd like to try it now, but I don't want to buy the whole thing again.